In-situ Measurement of Near-surface Soil Strength by the Fall-cone Device
1982
Bradford, J. M. | Grossman, R. B.
This study explored the use of the Swedish fall-cone device for insitu measurements of shear strength near the surface of soils. A laboratory fall-cone device was adapted for field use by replacing the original base and lengthening the cone stems. In-situ strengths were measured on selected soils in southwestern Iowa and southeastern Nebraska. A small increase in water potential resulted in a large decrease in shear strength. A heavier cone gave a lower strength value than a lighter cone. The near-surface strength of Sharpsburg soils in winter wheat fields was measured throughout the year. The strength immediately after fall planting was 10 to 20 kPa at about −3 kPa water potential. In the spring of 1980, largely because of consolidation from rainfall in the immediate post-thaw period, the strength was 30 to 50 kPa. In contrast, the spring of 1981 was dry and consolidation did not occur; consequently, there was no increase in strength from that immediately after planting.
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